Locking device for a mold group including a safety group

ABSTRACT

A closing device for a mold group with two half-molds extends along a main axis and has a device body mountable to one of the two half-molds, and a closing group having a closing element rotatable about a rotation axis between a closing position, in which the two half-molds are lockable and an opening position, in which the two half-molds are releasable. A movement group housed in the device body and engaged with the closing group to rotationally move the closing element has a stem movable along the main axis and transmission members for transforming linear motion of the stem into rotatory motion of the closing element. A command group has a command plate engaged with one command end of the stem and a metal sealing bellows engaged with the command plate. A position of the metal sealing bellows corresponds to an axial position of the command plate and of the stem.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application of PCT InternationalApplication No. PCT/IB2021/055536, having an International Filing Dateof Jun. 23, 2021 which claims the benefit of priority to Italian PatentApplication No. 102020000015061, filed Jun. 23, 2020, each of which ishereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a closing device for a mold group of amolding system, preferably of the rotational type. In addition, thepresent invention relates to a mold group of a molding system,preferably of rotational type, comprising at least one closing device.Furthermore, the present invention relates to a molding system,preferably of rotational type, comprising a mold group provided with atleast one closing device.

In particular, the present invention relates to the field of rotationalmolding of plastic materials; “rotational” molding means the moldingtechnique in which hollow products are made starting from polymers ofvarious kinds.

BACKGROUND OF THE INVENTION

The steps of the rotational molding technique and the rotational moldingequipment by means of which the technique is performed are well-known inthe prior art.

Indeed, the rotational molding technique firstly provides placing apredetermined amount of polymeric material in liquid or powder forminside a mold group. Subsequently, the mold group is moved, usually inrotation around two perpendicular axes, and at the same time it isobject of heating, so that the polymeric material inside the mold group,heated and moved, layers on the walls of the mold group itself. Finally,the mold group is cooled and, after it is reopened, the product isremoved.

The known mold groups typically consist of a plurality of componentsmutually joined to one another. Preferably, said components are known ashalf-molds. Said half-molds are typically joined by means of speciallyconformed and specially housed closing devices comprised in the moldgroup. In particular, said closing devices are integrally connected toone of the two half-molds and comprise at least one closing groupcontrollable in closing to perform the mutual engagement of the twohalf-molds or in opening to allow the mutual disengagement thereof.

A typical problem encountered in molding is related precisely to theefficiency of the aforesaid closing devices. Indeed, a series ofdrawbacks have been found on the known closing devices which affect thecorrect closing of the mold group itself. Such a situation isparticularly undesirable because it implies the production of anon-compliant product which must thus be discarded.

Furthermore, with particular reference to rotational molding, suchdrawbacks of the closing devices are because they are subject tomovement together with the half-molds but above all are involved in theheating and cooling operations and are thus subject to high thermalexcursions. Therefore, the known closing device solutions are subject tofrequent replacement and maintenance of their parts subject to wear andtear and/or breakage.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention toprovide a closing device for a mold group of a molding system,preferably of the rotational type, which solves the aforesaid drawbacks.

Such an object is achieved by a closing device, a mold group and amolding system, preferably of the rotational type, as described andclaimed herein.

Preferred variants implying further advantageous aspects are alsodescribed.

BRIEF DESCRIPTION OF THE FIGURES

Further features and advantages of the invention will be apparent fromthe description provided below of preferred embodiments thereof, givenby way of non-limiting examples, with reference to the accompanyingdrawings, in which:

FIGS. 1 and 1 a show a perspective view and a section perspective viewof a closing device, in a closing configuration, according to apreferred embodiment;

FIGS. 2 and 2 a show a perspective view and a section perspective viewof the closing device in FIGS. 1 and 1 a, in an opening configuration,according to a preferred embodiment;

FIG. 3 is a front view of the closing device in FIGS. 1 and 1 a;

FIGS. 3 a, 3 b, 3 c, and 3 d show some section views of the closingdevice taken along section planes A-A, B-B in FIG. 3 , and sectionplanes C-C and D-D in FIG. 3 a , respectively;

FIGS. 4, 4 a′ and 4 a″ show a perspective view and two section views ofa closing device, in a closing configuration, according to a preferredembodiment;

FIGS. 5, 5 a′ and 5 a″ show a perspective view and two section views ofa closing device in FIGS. 4, 4 a′ and 4 a″, in an opening configuration,according to a preferred embodiment;

FIG. 6 is a front view of the closing device in FIGS. 4, 4 a′ and 4 a″;

FIGS. 6 a, 6 b, 6 c, 6 d, 6 e, and 6 g show some section views of theclosing device taken along section planes A-A, B-B in FIG. 6 , andsection planes C-C, D-D, E-E, and G-G in FIG. 6 a , respectively;

FIG. 7 shows a diagrammatic of a rotational molding system whichcomprises a mold group, according to a preferred embodiment; and

FIG. 8 shows a mold group according to the present invention.

DETAILED DESCRIPTION

In the accompanying figures, reference numeral 1 indicates a closingdevice, according to the present invention.

The present invention further relates to a mold group 500 whichcomprises at least one closing device 1. Preferably, the mold group 500comprises two half-molds 510, 520.

Furthermore, it is a further object of the present invention a moldingsystem 900, preferably of the rotational type, comprising a mold group500 which in turn comprises at least one closing device 1.

According to a preferred embodiment, the molding system 900 comprises amachine 950 suitable for housing and moving the mold 500 group.Preferably, the machine 950 comprises a base frame which supports afirst movable frame 951 suitable for rotating about a first rotationaxis, e.g. vertical. Furthermore, the machine 950 preferably comprises asecond movable frame 952, supported by the first movable frame 951,wherein the second movable frame 952 is suitable for rotating about asecond preferably horizontal rotation axis.

According to a preferred embodiment, the machine 950 comprises firstmotion means suitable for moving the first movable frame 951 relative tothe base frame and second motion means suitable for moving the secondmovable frame 952 relative to the first movable frame 951.

According to a preferred embodiment, the mold group 500 can be housed onthe second movable frame 952.

According to a preferred embodiment, the system 900 comprises heatingmeans, such as an oven, suitable for heating the mold group 500.

According to a preferred embodiment, the system 900 comprises coolingmeans, e.g. fans, adapted to cool the mold group 500.

Furthermore, according to a preferred embodiment, the molding system 900further comprises air supplying means. Preferably, the air supplyingmeans are suitable for pneumatically supplying the closing device 1 inthe manner fully described below. Preferably, the air supplying meanscomprise appropriate conduits or pipes through which the air can besupplied to the closing device 1 or closing devices 1.

According to the present invention, the closing device 1 extends along amain axis X-X. Preferably, one portion is mountable integrally with onehalf-mold 510 and another portion is suitable for operating with theother half-mold 520.

Preferably, the axial end portion is mountable integrally with ahalf-mold 510, e.g. on its body or on a supporting frame in which thehalf-mold 510 is integrally housed.

According to the present invention, the closing device 1 comprises amain body 2.

Preferably, the main body 2 is mountable integrally with at least onehalf-mold 510, 520. Preferably, the main body 2 is suitable for entirelyhousing, partially housing and/or supporting the components describedbelow, comprised in the closing device 1 as described below and shown inthe figures by way of non-limiting example.

According to the present invention, the main body 2 is suitable forbeing connected to the air supplying means.

Indeed, the main body 2 preferably comprises a command chamber 25suppliable by the air supplying means. According to a preferredembodiment, the main body 2 comprises a supply port 250 fluidicallyconnected to the command chamber 25. Preferably, the supply port 250 isproximal to an axial end of the closing device 1. According to apreferred embodiment, the supply port 250 is positioned at the main axisX-X.

According to the present invention, the closing device 1 comprises afirst closing group 3 suitable for operating with a half-mold.

In particular, the closing group 3 is positioned at one end of thedevice body 2; preferably, the closing group 3 is positioned at the endof the device body 2 opposite to the end in which the command chamber 25is formed.

According to the present invention, the closing group 3 comprises atleast one closing element 30 rotatable about a rotation axis R-R betweena closing position and an opening position.

In the closing position, the closing element 30 is arrangedsubstantially orthogonal to the main axis X-X and the two half-molds510, 520 are mutually lockable.

In the opening position, the closing element 30 is arrangedsubstantially parallel to the main axis X-X and the two half-molds 510,520 are mutually releasable.

According to a preferred embodiment, the closing group 3 comprises a pinelement 31 extending along the rotation axis R-R.

Preferably, the closed element 30 is integrally connected to the pinelement 31.

According to a preferred embodiment, the closing group 3 comprises twoclosing elements 30 positioned at the axial ends of the pin element 31.

Preferably, the two closing elements 30 are movable in the same angularpositions relative to the rotation axis R-R. In other words, the twoclosing elements 30 are positioned mirroring each other.

According to a preferred embodiment, the pin element 31 is partiallyhoused in the main body 2, in a central portion thereof, so that theclosing elements 30 are engaged at the axial ends of the pin element 31which protrude from the main body 2.

According to the present invention, the closing device 1 furthercomprises a movement group 4 suitable for moving the closing group 3.

The movement group 4 is housed in the device body 2 and is operativelyconnected to the closing group 3, in particular to the pin element 31.

The movement group 4 comprises a stem 40 movable along the main axis X-Xand transmission members 41 engaged with the stem 40 and the closinggroup 3 suitable for transforming the linear motion of the stem intorotational motion of the pin element 31. In other words, an axialposition of the stem 40 corresponds to a specific angular position ofthe closing element 30.

Preferably, the transmission members 41 are engaged to a closing end 401of the stem 40 and to the pin element 31. Preferably, the transmissionmembers 41 comprise a cylindrical element 411 fixed to the closing end401, a rotation element 413 fixed to the pin element 31, and atransmission linkage 412 hinged to the cylindrical element 411 and therotation element 413.

According to the present invention, the closing device 1 comprises acommand group 5 suitable for commanding the movement, and consequentlythe axial position, of the stem 40.

The command group 5 is controllable by the air supplying means and issuitable for transmitting the action of the air supplying means to thestem 40.

Indeed, the command group 5 is housed in the command chamber 25comprised in the device body 2 in which the stem 40 is also at leastpartially housed.

The command group 5 comprises a command plate 50 engaged to a commandend 402 of the stem 40.

Furthermore, the command group 5 comprises a metal sealing bellows 51engaged with the command plate 50 so that a position of the metalsealing bellows 51 corresponds to an axial position of the command plate50, and thus of the stem 40.

Indeed, the metal sealing bellows 51 preferably divides the commandchamber 25 into two distinct half-chambers 251, 252 which are mutuallyseparated and sealed.

According to a preferred embodiment, with the metal sealing bellows 51compressed, the closing element 30 is in the closing position, whilewith the metal sealing bellows 51 extended, the closing element 30 is inthe opening position.

According to a preferred embodiment, the metal sealing bellows 51 isnormally in an extended position.

Preferably, in the absence of air thrust produced by the air supplyingmeans, the metal sealing bellows 51 is arranged in an extended position,and the closing group 3 in an open configuration.

Preferably, in the absence of air thrust produced by the air supplyingmeans, the metal sealing bellows 51 autonomously performs a returnaction towards the extended configuration. According to a preferredembodiment, by virtue of the presence of the metal sealing bellows 51and its mode of operation, there is no need for return means, e.g. suchas a coil spring, needed to return the command plate 50 and thus thestem 40, to an extended configuration, and thus of opening of theclosing group 3.

According to a preferred embodiment, the air supplying means aresuitable for creating a vacuum in the command chamber 25 to facilitatethe passage of the metal sealing bellows 51 between the compressedcondition and the extended condition.

According to a preferred embodiment, the metal sealing bellows 51extends about the stem 40.

Preferably, the metal sealing bellows 51 is located at a positionaxially opposite to the air inlet, i.e., is axially spaced apart fromthe supply port 250.

According to a preferred embodiment, the metal sealing bellows 51 isengaged at an end to the command plate 50, while at the other end, itcomprises a closing plate 52 suitable for axially closing the commandchamber 25.

Preferably, the stem 40 extends through the closing plate 52.

According to a preferred embodiment, the closing device 1 furthercomprises a safety group 6 suitable for operating on the movement group4 to lock it in a preferred configuration.

Preferably, in turn, the safety group 6 is controllable by the airsupplying means.

Preferably, the safety group 6 is adapted to operate on the stem 40 tolock and hold it in a preferred axial position.

According to a preferred embodiment, the safety group 6 extends along asafety axis Y-Y. Preferably, the safety axis is substantially orthogonalto the main axis X-X.

According to a preferred embodiment, a safety group 6 comprises a safetyelement 60 positionable in a safety position, in which it engages thestem 40 and keeps it in an axial position, and a release position, inwhich it is disengaged from the stem 40, which is free to move axially.

In other words, the safety group 6 is suitable for operating on the stem40 to inhibit or allow the axial movement thereof.

According to a preferred embodiment, the safety group 6 is positioned inan axial position between the command group 5 and the closing group 3.

Preferably, the safety group 6 engages the stem 40 in a region beforethe region in which the transmission members 41 are located.

Preferably, the safety group 6 comprises a metal safety bellows 61engaged to the safety element 60. Preferably, a position of the metalsafety bellows 61 corresponds to an axial position of the safety element60 and thus to whether or not the safety group 6 is engaged to themovement group 4.

According to a preferred embodiment, with the metal safety bellows 61compressed, the safety element 60 is in the safety position, and withthe metal safety bellows 61 extended the safety element 60 is in therelease position.

According to a preferred embodiment, the metal safety bellows 61 isnormally in a compressed position. In other words, in the absence ofaction of the air, the metal safety bellows 61 is extended and thesafety element 60 is in the released position.

In other words, the metal safety bellows 61 is suitable for operatingoppositely to the metal sealing bellows 51 (in the embodiments in whichit is provided).

According to a preferred embodiment, the safety group 6 is pneumaticallycommanded in the safety position to hold the closing group 3 in apreferred position, preferably in the closing position.

According to a preferred embodiment, the safety element 60 is of theband type, comprising an annular portion 600 which extends around thestem 40, wherein the safety position corresponds to the annular portion600 radially tightened onto the stem 40 and the release positioncorresponds to the annular portion 600 radially spaced apart from thestem 40.

According to a preferred embodiment, the main body 2 comprises a safetychamber 26 in which the metal safety bellows 61 is housed. Preferably,the safety element 60 is also at least partially housed in the safetychamber 26.

According to a preferred embodiment, the metal safety bellows 61comprises an end cap 612 at an axial end suitable for axially closingthe safety chamber 26 and a safety plate 611 integrally connected to thesafety element 60.

Preferably, the end cap 612 comprises an auxiliary supply port 260fluidically connected to the safety chamber 26. Preferably, theauxiliary supply port 260 is connectable to the air supplying means.

Additional embodiments of the closing device 1 are possible.

In particular, embodiments are possible in which the main body 2 is in asingle body, as well as embodiments (such as those shown in theaccompanying figures) in which the main body 2 consists of a pluralityof parts and portions.

Innovatively, the closing device, the mold which comprises said closingdevice, as well as the molding system described above, amply fulfill thescope of the present invention by solving the problems raised in typicalsolutions of the prior art.

Advantageously, the closing device maintains the locking position overtime.

Advantageously, the closing device resists the typical movements ofrotational molding.

Advantageously, the closing device resists the temperature changestypical of rotational molding.

Advantageously, the closing device has a limited number of components.

Advantageously, the closing device does not have specific sealingelements which are instead present in known closing device solutions.

Advantageously, the closing device shows an extremely longer life cyclecompared to the life cycle of known closing devices.

Advantageously, the closing device requires far less maintenance.

Advantageously, the closing device is pneumatically controllable in asimplified manner.

Advantageously, the mold group which comprises at least one closingdevice according to the above, in turn, achieves the aforesaidadvantageous technical effects.

Advantageously, in turn, the molding system, in which the mold groupmounts at least one closing device according to the description,achieves the above-mentioned advantageous technical effects.

Advantageously, the aforesaid technical effects are mainly found in arotational type molding system.

It is apparent that a person skilled in the art may make changes to theobject of the present invention, all contained within the scope ofprotection as defined in the following claims to satisfy contingentneeds.

1. A closing device for a mold group of a molding system, wherein themold group comprises two half molds, and wherein the closing deviceextends along a main axis and comprises: a device body mountable to oneof the two half-molds; a closing group, positioned at one end of thedevice body, comprising at least one closing element rotatable about arotation axis between a closing position, in which the at least oneclosing element is arranged substantially orthogonal to the main axisand the two half-molds are mutually lockable, and an opening position,in which the at least one closing element is arranged substantiallyparallel to the main axis and the two half-molds are mutuallyreleasable; a movement group housed in the device body and engaged withthe closing group to rotationally move the at least one closing element,wherein the movement group comprises a stem movable along the main axisand transmission members engaged with the stem and with the closinggroup, suitable for transforming a linear motion into a rotatory motion;a command group suitable for commanding an axial movement of the stem;and a safety group, extending along a safety axis substantiallyorthogonal to the main axis, the safety group being controllable by airsupplying means and comprising a safety element positionable in a safetyposition, in which the safety element engages the stem and keeps thestem in an axial position, and a release position, in which the safetyelement is disengaged from the stem, which is free to move axially. 2.The closing device of claim 1, wherein the safety group comprises ametal safety bellows engaged with the safety element, wherein, with themetal safety bellows compressed, the safety element is in the safetyposition, while with the metal safety bellows extended, the safetyelement is in the release position.
 3. The closing device of claim 1,wherein the safety element is of the band type and comprises an annularportion extending around the stem, and wherein the safety positioncorresponds to the annular portion radially tightened onto the stem andthe release position corresponds to the annular portion radially spacedapart from the stem.
 4. The closing device of claim 1, wherein thecommand group is housed in a command chamber comprised in the devicebody, the command group being controllable by the air supplying meansand comprising a command plate engaged with a command end of the stemand a metal sealing bellows engaged with the command plate so that to aposition of the metal sealing bellows corresponds an axial position ofthe command plate and of the stem.
 5. The closing device of claim 4,wherein, with the metal sealing bellows compressed, the at least oneclosing element is in the closing position, while with the metal sealingbellows extended, the at least one closing element is in the openingposition.
 6. The closing device of claim 4, wherein the metal sealingbellows extends around the stem.
 7. The closing device of claim 4,wherein the metal sealing bellows is, at one end, solidly connected tothe command plate, and at the other end the metal sealing bellowscomprises a closing plate suitable for axially closing the commandchamber.
 8. The closing device of claim 1, wherein the closing groupcomprises a pin element extending along the rotation axis, wherein theat least one closing element is solidly fixed to the pin element, andwherein the movement group acts upon the pin element.
 9. The closingdevice of claim 8, wherein the closing group comprises two closingelements positioned at axial ends of the pin element.
 10. A mold groupof a molding system, comprising two half-molds and at least one closingdevice according to claim
 1. 11. A molding system, comprising a moldgroup comprising two half-molds and at least one closing deviceaccording to claim
 1. 12. The closing device of claim 1, wherein themolding system is of rotational type.